Semiconductor device and method for manufacturing semiconductor device

ABSTRACT

A method for manufacturing a semiconductor device having flat pads. An opening and island-like dielectric films are first formed in a dielectric film. The opening is then filled with metal, and a metal layer is formed on the dielectric film. The upper surface of the metal layer is flattened using the CMP technique with the upper surface of the dielectric film functioning as a stopper. The island-like dielectric films prevent the occurrence of dishing in a conductive portion.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device. More particularly, the present invention relates to a semiconductor device having an external electrode terminal formed using the Damascene technique and a method for manufacturing such a semiconductor device.

[0002] Due to the increased integration, density, and speed of semiconductor devices, wiring that enables higher performance is desired. In the prior art, the material used for wiring is mainly aluminum. However, there is a tendency of electromigration occurring when using aluminum wires. Accordingly, copper has gathered attention as a material that has lower resistance than aluminum and resists electromigration. Copper wires contribute to increasing the speed of semiconductor devices and prolonging the life of semiconductor devices.

[0003] In the prior art, copper wires are manufactured using the Damascene technique. A groove is first formed in a dielectric film having a flat surface. The groove is then filled with a metal material. The metal material is then flattened so that the upper surface of the metal material becomes flush with the surface of the dielectric film. This manufactures metal wires. Accordingly, the Damascene technique is a relatively simple method for manufacturing metal wires and easily manufactures copper wires, which cannot be formed through dry etching.

[0004] In the prior art, a chemical mechanical polish (CMP) technique is used to flatten the metal material. The CMP technique is a process that combines etching and mechanical polishing and is optimal for flattening relatively large areas. A flattened semiconductor device is manufactured using the Damascene technique to form wires and using the CMP technique to flatten each layer of the semiconductor device.

[0005] As shown in FIG. 1, in an integrated circuit of a semiconductor device, an external electrode terminal, such as pad P, is larger than other wires. It is thus difficult to form a flat pad P when using the CMP technique and the Damascene technique.

[0006] The pad P is an electrode for connecting a substrate, on which an integrated circuit is formed, to an external circuit. The pad P is connected to the external circuit by a wire w and a lead frame L. As shown in FIG. 2, the pad P includes a lower pad P1, an intermediate pad P2, and an upper pad P3. The size B of each of the pads P1, P2, P3 is larger than the size A of an element in the integrated circuit. In the actual semiconductor device, the size B of the pads P1, P2, P3 is several hundred times larger than the size A of the element.

[0007] The lower pad P1 and the intermediate pad P2 are not directly connected to the wire w but have the same size as the upper pad P3. This is to connect the upper pad P3 to the intermediate and lower pads P1, P2 in an aligned state and to test the contact between the semiconductor device and the external device with the lower and intermediate pads P1, P2 before forming an upper wiring layer.

[0008] A method for forming the relatively large pads P1, P2 using the Damascene technique at the same time as when forming an element region will now be discussed.

[0009] A groove formed in a dielectric film is first filled with a metal material of the pads P1, P2, P3. The upper surfaces of the pads P1, P2, P3 are then flattened using the CMP technique. However, the upper surface of the metal filled in the groove, which has a relatively large opened area, becomes lower than the surface of the dielectric film. This is a problem unique to the CMP technique and is referred to as dishing. Dishing decreases the flatness of the semiconductor device. Further, when the upper layer undergoes a lithography process, dishing may hinder focusing.

[0010] A prior art pad forming process and its shortcoming will now be discussed in more detail with reference to FIGS. 3a to 3 g.

[0011] Referring to FIG. 3a, in the prior art, a dielectric film 110 is first deposited on a substrate 101. A relatively large pad formation region 110 h is formed in the dielectric film 110. Copper 111′ is applied to the dielectric film 110 and the substrate 101 and filled in the pad formation region 110 h.

[0012] Then, the upper surface of the copper 111′ is flattened using the CMP technique to form a pad 111 with the dielectric film 110 functioning as a stopper film. In this state, as shown in FIG. 3b, dishing occurs in the copper 111′ in the pad formation region 110 h, or the pad 111. Thus, the upper surface of the pad 111 is not flush with the upper surface of the dielectric film 110.

[0013] Further, when forming another layer on the pad 111 and the dielectric film 110 to manufacture a semiconductor device having a multilayer structure, dishing decreases the flatness of each layer.

[0014] A process for manufacturing a semiconductor device having a multilayer structure will now be discussed with reference to FIGS. 3c to 3 e. An interlayer dielectric film 120 is formed on the pad 111 and the dielectric film 110 (FIG. 3c). Contact holes 121 are then formed in the interlayer dielectric film 120 (FIG. 3d). A metal layer 122′ is then applied to the interlayer dielectric film 120 so that the contact holes 121 are filled with metal, which is used to form plugs 122 (FIG. 3e). The metal layer 122′ is etched to form the plugs (FIG. 3f). As shown in FIG. 3g, a pad 131, which is connected to the plugs 122, is formed. The lower layer pad 111 is connected to the upper layer pad 131 by the plugs 122.

[0015] Dishing also occurs when forming elements other than the pads 111, 131 using the Damascene technique. Thus, the flattening of a flat semiconductor device is difficult.

SUMMARY OF THE INVENTION

[0016] It is an object of the present invention to provide a method for manufacturing a semiconductor device having a flat surface using the Damascene technique and to provide a flat semiconductor device.

[0017] To achieve the above object, the present invention provides a semiconductor device that includes a semiconductor substrate. At least one dielectric film is arranged on the substrate and that dielectric film has an opening. A conductive portion fills the opening. At least one dielectric member is embedded in the conductive portion that fills the opening.

[0018] A further perspective of the present invention is a method for manufacturing a semiconductor device. The method includes forming an opening in a dielectric film arranged above the semiconductor substrate so as to leave a projection in the opening, filling the opening with a metal, and flattening the surface of the metal using the upper surface of the dielectric film as a stopper.

[0019] A further perspective of the present invention is a semiconductor device including a semiconductor substrate. At least one dielectric film is arranged on the substrate. The dielectric film includes an upper surface, a lower surface, and an opening. At least one dielectric member is arranged in the opening. A conductive portion fills the opening so as to surround the at least one dielectric member.

[0020] A further perspective of the present invention is a method for manufacturing a semiconductor device having a dielectric film arranged above a semiconductor substrate. The method includes forming an opening in the dielectric film so as to leave a projection in the opening by removing part of the dielectric film, filling the opening with a metal, and flattening the metal so that the upper surface of the dielectric film is flush with the upper surface of the metal.

[0021] Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0023]FIG. 1 is a schematic perspective view showing pad of a typical semiconductor device;

[0024]FIG. 2 is a schematic cross-sectional view showing a typical pad and an element of the prior art;

[0025]FIGS. 3a-3 g are cross-sectional views illustrating a prior art process for manufacturing a semiconductor device;

[0026]FIG. 4 is a cross-sectional view showing a semiconductor device according to a preferred embodiment of the present invention;

[0027]FIG. 5 is a plan view showing a pad of the semiconductor device of FIG. 4; and

[0028]FIGS. 6a-6 f are cross-sectional views illustrating a process for manufacturing the semiconductor device of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] A semiconductor device 100 according to a preferred embodiment of the present invention will now be discussed.

[0030] Referring to FIG. 4, the semiconductor device 100 includes a semiconductor substrate 1, insulation films or dielectric films 10, 20, 30, which are formed on the semiconductor substrate 1, and external electrode terminals, or pads 11, 31. The lower pads 11 are formed in the lower dielectric film 10 of the semiconductor substrate 1, and the upper pads 31 are formed in the upper dielectric film 30. The lower dielectric film 10 and the lower pad 11 define a lower wiring layer, and the upper dielectric film 30 and the upper pad 31 define an upper wiring layer. An interlayer dielectric film 20 is formed between the lower and upper wiring layers. Further, the interlayer dielectric film 20 has contact holes 21. A contact wire, or a plug 22, is arranged in each contact hole 21. The upper wiring layer, the lower wiring layer, and the interlayer dielectric film 20 are formed when other corresponding wiring layers (not shown) and interlayer dielectric films (not shown) of an integrated circuit in the semiconductor device 100 are formed.

[0031] The lower and upper pads 11, 31 are formed in the lower and upper dielectric films 10, 30, respectively. With reference to FIG. 5, each lower pad 11 includes a metal conductive portion 11 m and island-like dielectric films 11 i, each of which are encompassed by the conductive portion 11 m. The island-like dielectric films 11 i are arranged in an opening 11 g separated from one another. The height of each island-like dielectric film 11 i, or each projection, is equal to the thickness of the lower wiring layer 10. In other words, the top end and bottom end of each island-like dielectric film 11 i are respectively flush with the upper surface and lower surface of the lower wiring layer 10. The conductive portion 11 m is formed using the Damascene technique. Although the lower pad 11 has the island-like dielectric films 11 i, the conductive portion 11 m is not divided by the island-like dielectric films 11 i and thus conducts electricity. In other words, the island-like dielectric films 11 i do not electrically disconnect parts of the conductive portion 11 m from other parts of the conductive portion 11 m.

[0032] The upper pad 31 has the same structure as that of the lower pad 11. That is, each upper pad 31 includes a conductive portion 31 m, which is made of a metal such as copper, and island-like dielectric films 31 i, which are arranged in the conductive portion 31 m. The height of each island-like dielectric film 31 i is equal to the thickness of the upper wiring layer 30. It is preferred that the area of the lower pad 11 and the upper pad 31 be substantially the same. This facilitates alignment and connection of the upper pad 31 with the lower pad 11.

[0033] The lower and upper pads 11, 31 have the island-like dielectric films 11 i, 31 i. This prevents dishing from occurring in the conductive portions 11 m, 31 m. Thus, the surfaces of the lower and upper pads 11, 31 are flattened when performing the CMP technique. Further, when performing the Dual Damascene technique to form a wiring layer of an integrated circuit in the semiconductor device 100, the pad 31 and contact holes 21 are simultaneously formed. Since the island-like dielectric films 11 i, 31 i prevent dishing from occurring, the semiconductor device 100 is manufactured with a flat surface.

[0034] The lower and upper pads 11, 31 are provided with dielectric members, or the island-like dielectric films 11 i, 31 i. Thus, the lower pad 11 and the upper pad 31 are connected together in an optimal manner. Further, wires that are connected to an external circuit are connected to the upper pad 31 in an optimal manner. More specifically, the plugs 22, which connect the conductive portion 11 m of the lower pad 11 and the conductive portion 31 m of the upper pad 31, electrically connect the lower and upper pads 11, 31. The area of the upper surfaces of the island-like dielectric films 11 i is smaller than that of the contact area between the wire and the upper pads 31. Thus, the electric connection between the upper pad 31 and the wire is satisfactory.

[0035] When the structure of the upper pad 31 is the same as that of the lower pad 11, the lower wiring layer 10 may be tested before forming the interlayer dielectric film 20 through the lower pad 11 and a wire by an external testing apparatus (not shown).

[0036] A process for manufacturing the semiconductor device 100 of the preferred embodiment will now be discussed with reference to FIGS. 6a-6 f. FIGS. 6a-6 f show only the vicinity of the pads 11, 31 of the semiconductor device 100. It is preferred that the pads 11, 31 be formed in the same process as other wiring layers and interlayer dielectric films of the integrated circuit (not shown).

[0037]FIGS. 6a and 6 b illustrate a process for manufacturing the lower pad 11 using the Damascene technique. More specifically, as shown in FIG. 6a, the lower dielectric film 10 is first formed on the substrate 1. The opening 11 g is formed so that the island-like dielectric films 11 i are left in the lower dielectric film 10. This defines a pad formation region 11 h. A metal 11 m′ is applied to the substrate 1 and the dielectric film 10. This fills the opening 11 g with the metal 11 m′.

[0038] For example, copper, aluminum alloy, or tungsten may be used as the metal 11 m′. The metal 11 m′ is applied to the substrate 1 and the dielectric film 10 by performing, for example, plating, high temperature sputtering, or the CVD process.

[0039] Then, the CMP technique is performed to flatten the upper surface of the metal 11 m′ using the upper surface of the lower dielectric film 10 as a stopper film. This forms the lower pad 11, which includes the conductive portion 11 m and the island-like dielectric films 11 i.

[0040]FIGS. 6c-6 f illustrate a process for forming the plug 22 in the interlayer dielectric film 20 using the Damascene technique. Referring to FIG. 6c, the interlayer dielectric film 20 is formed on the lower dielectric film 10 and the lower pad 11. Referring to FIG. 6d, the contact holes 21 are formed in the interlayer dielectric film 20 at positions corresponding to the conductive portion 11 m. Referring to FIG. 6e, a metal 22′ is applied to the interlayer dielectric film 20 so that the contact holes 21 are filled with the metal 22′. Referring to FIG. 6e, the CMP technique is used to flatten the upper surface of the metal 22′ with the interlayer dielectric film 20 functioning as a stopper. This forms the plugs 22 in the contact holes 21.

[0041] The same material as the metal 11 m′ of the lower layer may be used as the metal 22′. Further, the metal 22′ may be applied to the interlayer dielectric film 20 in the same manner as when the metal 11 m′ is applied to the lower dielectric film 10.

[0042] After forming the plugs 22, the upper dielectric film 30 and the upper pads 31 are formed on the interlayer dielectric film 20 and the plugs 22. The upper dielectric film 30 and the upper pad 31 are formed in the same manner as the lower dielectric film 10 and the lower pad 11.

[0043] In the present specification, electrodes and wires, such as the pads, define conductive bodies.

[0044] The preferred embodiment has the advantages described below.

[0045] (1) The island-like dielectric films 11 i, 31 i, which are formed in the pads 11, 31, prevent the occurrence of dishing in the conductive portions 11 m, 31 m, respectively. Further, the island-like dielectric films 11 i, 31 i are separated from one another in the corresponding pads 11, 31. Additionally, the conductive portions 11 m, 31 m are not divided by the corresponding island-like dielectric films 11 i, 31 i. Since the conductive portions 11 m, 31 m are each formed integrally, the reliability of the pads 11, 31 as a wire is maintained.

[0046] (2) The lower pads 11 and the upper pads 31 have substantially the same size. Thus, the lower and upper pads 11, 31 are easily aligned and connected to each other. Further, after forming the lower pad 11, an external testing apparatus may be connected to the lower pad 11 to test wire layers formed before the lower pad 11.

[0047] It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms.

[0048] As long as the lower pads 11 can be connected to the upper pads 31, the lower pads 11 may be formed smaller than the upper pads 31 to prevent the occurring of dishing with the lower pads 11.

[0049] The island-like dielectric films 11 i may be provided only for the lower pad 11. This prevents or suppresses the occurrence of dishing in the lower pad 11 and manufactures a relatively flat semiconductor device 100. When the island-like dielectric films 31 i are not necessary, it is preferred that a process other than the Damascene technique be used to form the upper pad 31.

[0050] Each of the island-like dielectric films 11 i, 31 i do not have to have a square upper surface like in FIG. 5. For example, the island-like dielectric films 11 i, 31 i may each have a rectangular upper surface. In this case, the island-like dielectric films 11 i, 31 i are arranged in a stripe-like manner.

[0051] Instead of the island-like dielectric films 11 i, 31 i, at least one insulator or dielectric member having any shape, such as a cylindrical shape, may be formed in the openings 11 g, 31 g. This also avoids or suppresses the occurrence of dishing in the pads 11, 31. However, if the dielectric member in each conductive portion 11 m, 31 m divides part of the conductive portions 11 m, 31 m from other parts, the dielectric member would electrically disconnect the divided parts in each conductive portion 11 m, 31 m.

[0052] Instead of the semiconductor device 100, which has a plurality of wiring layers, the pads 11, 31 of the preferred embodiment and the method for manufacturing the pads 11, 31 may be applied to a semiconductor device having any number of layers including, a single-layer structure semiconductor device. All of the pads in the semiconductor device are not required to have the island-like dielectric films 11 i, 31 i. The island-like dielectric films 11 i, 31 i are formed only on pads that are fabricated using the Damascene technique.

[0053] The pads 11, 31 do not have to be formed when forming the wiring layers in the integrated circuit of the semiconductor device 100.

[0054] The application of the present invention is not limited to the formation of the pads 11, 31 and the plugs 22. The present invention may also be applied when forming wires and electrodes (conductive bodies) using the Damascene process. This also prevents or suppresses the occurrence of dishing in the wires and electrodes (conductive bodies). For example, a conductive portion, such as the conductive portion 11 m of the pad 11, may be formed in lieu of the plugs 22. More specifically, an opening may be formed in the interlayer dielectric film 20 leaving at least one insulator, or dielectric projection, in the opening. The size of the opening is substantially the same as that of the lower pad 11 and the upper pad 31. The opening is filled with metal to connect the lower pad 11 and the upper pad 31.

[0055] The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

What is claimed is:
 1. A semiconductor device comprising: a semiconductor substrate; at least one dielectric film arranged on the substrate and having an opening; a conductive portion filling the opening; and at least one dielectric member embedded in the conductive portion that fills the opening.
 2. The semiconductor device according to claim 1, wherein the at least one dielectric member is arranged in an island-like manner in the opening.
 3. The semiconductor device according to claim 1 having a multilayer wiring structure including a lower wiring layer, which is arranged on the semiconductor substrate, wherein the conductive portion is formed in the lower wiring layer.
 4. The semiconductor device according to claim 1, wherein the conductive portion includes an external electrode terminal.
 5. A method for manufacturing a semiconductor device comprising: forming an opening in a dielectric film arranged above the semiconductor substrate so as to leave a dielectric projection in the opening; filling the opening with a metal; and flattening the surface of the metal using the upper surface of the dielectric film as a stopper.
 6. A semiconductor device comprising: a semiconductor substrate; at least one dielectric film arranged on the substrate and including an upper surface, a lower surface, and an opening; at least one dielectric member arranged in the opening; and a conductive portion filling the opening so as to surround the at least one dielectric member.
 7. The semiconductor device according to claim 6, wherein the dielectric member has a height that is the same as the thickness of the dielectric film.
 8. The semiconductor device according to claim 6, wherein the dielectric member has an end flush with the upper surface of the dielectric film and a further end flush with the lower surface of the dielectric film.
 9. The semiconductor device according to claim 6, wherein the at least one dielectric member is one of a plurality of separated dielectric members.
 10. The semiconductor device according to claim 6, wherein the conductive portion has a flat surface flush with the upper surface of the dielectric film.
 11. A method for manufacturing a semiconductor device comprising: forming a dielectric film arranged above a semiconductor substrate; forming an opening in the dielectric film so as to leave a dielectric projection in the opening by removing part of the dielectric film; filling the opening with a metal; and flattening the metal so that the upper surface of the dielectric film is flush with the upper surface of the metal. 